The invention relates to a method of photographically recording and three-dimensionally reproducing an object so as to present different views of the object as considered from the directions of differently located observers.
It is well known to use a camera having an objective and a diaphragm to record an object on a photographic plate or film. A narrow section of the light radiating from the object is received for recording purposes, corresponding to a certain viewpoint, making for a one-viewpoint method. Furthermore, by setting the distance between the photographic plate and the objective in correspondence to a desired sharpness setting, it is essentially a single object plane or a single strip of object space which is projected onto the photographic plate. The rest of the information contained in the object light is lost, and accordingly a photographic plate exposed in this way and thereafter developed produces an image which, in the first place, corresponds to a single viewpoint and which, in the second place, does not have any three-dimensional effect.
Three-dimensional (stereoscopic) methods are known in which each eye of the human observer sees only an associated half of the total image, with a three-dimensional impression resulting in the mind of the human viewer as a result of fusing of the two half images. These methods involve synchronized operation of two cameras which are spaced apart a distance corresponding to normal eye spacing; upon subsequent reproduction of the recorded image, steps must be taken to assure that each eye of the viewer receives only the associated half of the total image. These known methods are accordingly quite expensive. However, in contrast to the one-viewpoint methods referred to above, a certain three-dimensional character is achieved. These stereoscopic methods can be characterized as a special case of two-viewpoint methods, but with the exception that the spacing of the cameras to correspond to eye spacing still leads, in the end, to only a single view of the object as a whole. In any event, the human viewer of the reproduction is confined to a single position relative to the three-dimensional object whose image is being viewed.
An entirely different three-dimensional recording technique involves the use of holography. This involves the reproducible storing of the light-wave field emanating from an illuminated object in the form of a hologram somewhat comparable to a photographic plate. What is actually recorded is an interference pattern between a bundle of light rays emanating from an illuminated object and a bundle of reference light rays emanating from the source of illumination. The use of storable information derived from interference phenomena necessitates the use of a source of coherent light, in the form of a laser, for both recording and reproduction purposes. For color or multicolor recording and reproduction, a plurality of corresponding monochromatic laser light sources are required. The need for laser light sources, which are very expensive and low in efficiency compared to the equipment needed for daylight and artificial-light photography, seriously limits the present use and future prospects of holographic three-dimensional picture taking and reproduction.
The insufficient illumination attributable to the low-efficiency operation of laser light sources is one of the main reasons for the shadowy and unnatural appearance encountered in holographic reproduction. Furthermore, the short wavelength of the light in question, plus the use of interference phenomena to effect information storage, make for a very marked sensitivity of the holographic picture to motion of any kind. This makes holography of very little use for making pictures of animate objects. On the other hand, holography does constitute a true multi-viewpoint recording method in which the human viewer can observe the reproduced object from different sides, and even from all sides (360.degree. holos). The present stage of the holographic art is such that objects larger than about 2 .times. 2 .times. 2 m cannot be holographed.